This invention is directed to a digital watch which employs a multiplex signal processing circuit on a C/MOS chip with a liquid crystal digital horological display.
The employment of an electronic oscillator to produce pulses which are processed to drive a digital watch display is broadly old. There are a number of publications on this subject, and these include an article entitled "C/MOS Digital Wrist Watch Features Liquid Crystal Display" by N. A. Luce, Electronics, Apr. 10, 1973, pages 93 through 97. Another short news item is entitled "TI's Liquid Crystal Set for Digital Watch" which appears in Electronics, Apr. 24, 1972, at page 42. A review or overview article entitled "The Electronic Watch" by Marce Eleccion appears in IEEE/Spectrum, April 1973, at pages 24 through 32. The two Electronics articles teach that liquid crystals must be continuously energized, and thus there must be a liquid crystal display device for each of the types of information which are to be displayed. Thus, when a large number of displays are desired, as in the Apr. 24, 1972 Electronics article, the electronic circuitry must continually process all of this information to maintain the display. The continuously operating circuitry within the watch must be adequate and complete enough to continuously calculate and store all of this information and also drive the display itself.
With light emitting diode displays, it was found that multiplexing of signals could be employed to reduce the circuit complexity by reducing the number of decoders between the counters and the light-emitting diode displays. This is because the multiplexing of the signal, while causing high cyclic rate energization of the light-emitting diodes, still provides an acceptable diode output signal. However, at present liquid crystals cannot be driven directly from a multiplexed signal, because each segment requires continuous drive.